Emma has 25% as many pens as Mary. Mary has 130% as many pens as Risa. If Mary gives 12 pens to Risa, both will then have an equal number of pens. Find the average number of pens the three of them have.

Emma	Mary	Risa
1x13	4x13
	13x4	10x4
13 u	52 u	40 u

25% = ²⁵₁₀₀ = ¹₄
130% = ¹³⁰₁₀₀= ¹³₁₀

The number of pens that Emma has is repeated.  Make the number of pens that Emma has the same. LCM of 4 and 13 is 52.

	Mary	Risa	Total
Before	52 u	40 u	92 u
Change	- 6 u	+ 6 u
After	46 u	46 u	92 u

Total number of pens that Mary and Risa have
= 52 u + 40 u
= 92 u

After Mary gives to Risa, both of them will have the same number of pens. 

The total number of pens that Mary and Risa have remains unchanged.

Number of pens that each of them will have
= 92 u ÷ 2
= 46 u

Number of pens that Mary gives to Risa
= 52 u - 46 u
= 6 u

6 u = 12

1 u = 12 ÷ 6 = 2

Total number of pens that three of them have
= 92 u + 13 u
= 105 u

Average number of pens that each of them have
= 105 u ÷ 3
= 35 u
= 35 x 2
= 70

Answer(s): 70